Field of the Invention
This invention relates to data compression/transfer/decompression systems, and more particularly relates to a symmetrical adaptive data compression/transfer/decompression system where both sender and receiver dynamically with respect to the data stream carry out adaptive prediction calculation regimens, presenting for binary decision symmetrical sequences of predictions representing data streams at source and destination, calculating compression/decompression decision predictions separately but symmetrically at source and destination for binary decisions 1 . . . n according to cumulative prediction history which is for each decision optimized respectively for decisions 0 . . . n-1.
The system operates by adaptively coding the binary decisions rather than being forced to send a bit. Since the statistics used for the coding of the nth decision are part of the adaption process carried out symmetrically by the source model and destination model updated to the n-1th decision, optimal coding for the model selected is achieved without constraint as to the type of data transferred or the model selected.
All information transferred according to this invention is compressed for transfer, without requiring the overhead of transferring any probability information, because predicted probabilities are calculated symmetrically at source and destination, using adaptive techniques.
For reasons of speed, it is advantageous in some circumstances to delay updating of the probability information. This delay is useful for processing an event which occurs many times in succession; since updating a counter is cheaper than the multiplication required to update the probability, the coder operates more rapidly.
The length of the total compressed data stream approaches the entropy predictions, even with relatively small data processors, such as those operating with 16 bit precision.